This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-148459 filed on May 19, 2000.
1. Field of the Invention
The present invention relates to a semiconductor device mount structure in which a semiconductor device is mounted to a heat dissipating member.
2. Description of Related Art
One previously proposed semiconductor device mount structure is schematically shown in FIG. 5. A semiconductor device 20 is constructed as a package in which a semiconductor chip 21, such as a power MOSFET, that generates substantial heat upon operation thereof is encapsulated within a resin encapsulating material through a molding process. A heat dissipating member (fins) 10 is made of a highly heat conductive material, such as copper or aluminum. The semiconductor device 20 is secured to a mounting surface of the heat dissipating member 10 by a screw 100. Leads 22 extend out from the semiconductor device 20 and are electrically connected to a printed circuit board (not shown).
An interface member 30, such as a heat conductive grease material or a heat conductive sheet material, is placed between the semiconductor device 20 and the heat dissipating member 10. Heat generated from the semiconductor chip 21 is conducted to the heat dissipating member 10 through the interface member 30. Then, the heat conducted to the heat dissipating member 10 is dissipated from the heat dissipating member 10, for instance, into the atmosphere.
Since the semiconductor device 20 is secured to the heat dissipating member 10 by the screw 100, the heat dissipating property is greatly influenced by a type of material used for the heat dissipating member 10, a flatness of the mounting surface of the heat dissipating member 10, a screw torque of the screw 100 or the like. Thus, it is difficult to achieve a stable good heat dissipating property (low heat resistance).
That is, as shown in FIG. 6, the screw 100 is not located right above the heat source (mainly the semiconductor chip 21) to bias the heat source against the heat dissipating member 10. Thus, when the screw 100 is tightened, a bottom side of the semiconductor device 20 below the heat source can be lifted from the heat dissipating member 10, so that the heat resistance between the semiconductor device 20 and the heat dissipating member 10 is increased.
Furthermore, in such a mount structure using the screw 100 for securing the semiconductor device 20, the contact between the semiconductor device 20 and the heat dissipating member 10 is greatly influenced by the flatness of the mounting surface of the heat dissipating member 10. In addition, if the heat dissipating member 10 is made of a soft material, such as copper, the tightening of the screw 100 may cause deformation of the mounting surface of the heat dissipating member 10. Thus, the bottom side of the semiconductor device 20 below the heat source may be lifted or spaced from the heat dissipating member 10.
Also, in the mount structure shown in FIG. 5, the circuit board (not shown) to which the leads 22 are connected is arranged above the semiconductor device 20. Thus, the semiconductor device 20 mounted to the heat dissipating member 10 is positioned between the heat dissipating member 10 and the circuit board. As a result, the heat dissipated from the semiconductor device 20 may affect the performance of the circuit board.
The present invention addresses the above disadvantages. Accordingly, it is an objective of the present invention to provide a semiconductor device mount structure that achieves stable effective heat dissipating property and restrains influences of heat radiated from a semiconductor device on a circuit board arranged above the semiconductor device.
To achieve the objective of the present invention, there is provided a semiconductor device mount structure including a heat dissipating member, a circuit board, a semiconductor device and a leaf spring member. The heat dissipating member has a mounting surface. The circuit board is opposed to the mounting surface of the heat dissipating member. The semiconductor device is mounted to the mounting surface of the heat dissipating member. The semiconductor device is electrically connected to the circuit board. The leaf spring member is arranged between the semiconductor device and the circuit board in such a manner that the leaf spring member biases the semiconductor device against the mounting surface of the heat dissipating member. The leaf spring member has a heat insulating material integrated on one side thereof which faces the circuit board.
The semiconductor device may includes a heat generating element, such as a power MOSFET. The leaf spring member may resiliently contacting the semiconductor device on a portion of a surface of the semiconductor device, which is located along a line that extends perpendicular to the mounting surface of the heat dissipating member and that passes through the heat generating element.